If add MIXIM module in OMNET++, which is for wireless sensor network contains 802.15.4.

This  standard has been implemented in Castalia.

Thank you Muhsin and Ayaz....I will try your suggestion

Does the 802.15.4 module includes Guaranteed Time Slot (GTS) mechanism? 

Yes it does. You can read the code and see that which features are implemented and which are not.  The code  is very well written and well commented.

Hi

Please, I am now trying to implement (WSN clustering + SDN) with 802.15.4,, but I am not sure if omnet++ is the suitable tool ,, or ns2 is better??

does I need to use castalia with omnet!!! or I can use it without castalia??

Note:: I need to implement my own work without Zigbee to make some improvements in routing side.

Regards

Mais